There was a deafening crash. To quote Brian Strong's words: "It was as if the entire contents of an ironmonger's store had been dropped from the top of a skyscraper". A cloud of dust and smoke rose high in the air, mingled with fragments of jagged iron. Flames fifty feet in height shot up from the pipe, spreading far and wide as the inexhaustible supply of highly inflammable oil poured out in torrents to add to the work of destruction. "That's kippered the show," remarked Peter gleefully, as the two Englishmen retraced their steps to the flying-boat. The next business was to "pay off" the Rioguayan engineer. He was given a supply of provisions and a liberal quantity of tobacco and told to clear out and not to hurry back to San Antonio; while, for self-protection, he was provided with a rifle and twenty rounds of ammunition. "You might have made him start up the motors, Peter," remarked his uncle, as the mechanic disappeared in the undergrowth. "Thought I'd try my hand at the job," replied his nephew. The for'ard pair of motors fired without hesitation, but the after ones gave a certain amount of trouble. At length, with the four engines throbbing and out of gear, Peter made his way to the pilot's seat. At a steep angle, the flying-boat rose skywards. As she did so, a rifle bullet "pinged" harmlessly against the light steel armour plating of the fuselage. "Ungrateful brute, that mechanic," was Peter's only remark. Ten minutes later the fiercely burning oil pipe was a mere speck in the distance. The flying-boat, at an altitude of three thousand metres, was heading for the distant Sierras, that rose in a far-flung barrier of irregular projection to a height averaging nine thousand feet above the sea-level. The aircraft was flying "all out", her speed, on account of the rarefaction of the atmosphere, being a little less than 140 miles an hour. Peter was in a hurry. It was most desirable that the mountains should be crossed well before dark. Apart from the risk of crashing blindly against one of the many almost vertical peaks, there were the dangerous air-pockets and eddies to be taken into consideration, and with the setting of the sun, and the consequent rapid cooling of the earth's surface, the higher altitudes were certain to be disturbed by raging winds that attain the velocity of a hurricane. For miles the ground rose steadily. Viewed from a height, the rise appeared to be gradual, since the smaller irregularities were apparently flattened out. It was only by judging by the shadows cast by the sun, which was now well down in the west, that the numerous valleys and ridges could be noticed. For the first hundred miles, the country was well wooded. Then came a wide belt of grass land, gradually merging into an arid waste absolutely destitute of vegetation. The desert marked the beginning of the Sierras, which were now plainly visible at a distance of thirty or forty miles.